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Tuesday, January 31, 2012

Did Darwin run a pyramid scheme? Darwinian method, continued

Before the period of the Enlightenment in science, roughly starting with Francis Bacon and Galileo and others, about 400 years ago, a model of knowledge (among scientific types, at least, not farmers and craftsmen and others who actually earn a living) was largely attributed to Aristotle from around 400 BC. According to this view of how we should figure out the world, we were hard-wired to understand the nature of Nature (sounds like a lot of genetic or Darwinian determinists, doesn't it?). Thus, knowledge could be deductive (the classic example of this is 1) All men are mortal, 2) Socrates is a man, 3) Therefore, Socrates is mortal). The basic truths were known and were in that sense axioms from which predictions about facts to be found could be deduced. In a sense, the facts were latent in the assumptions. A theory came first, and led to many facts. (The BBC Radio 4 program, In Our Time, featured a nice discussion of the Scientific Method last week.)

But the Enlightenment turned that idea on its head. The idea was the scientific method that started with observation rather than inspiration, and built up a pyramid of understanding. First, by the process of induction, many observations were made, seen to be consistent, and they lay at the base of knowledge (All the swans I've ever seen are white, therefore all swans are white). Other types of generalization built upon this base, to the top of a pyramid of understanding, the final theory that we infer from facts.

When Darwin published his theory of evolution, of descent with modification screened by natural selection, from a common ancestral form, it was a challenge to accepted wisdom. The scientific method was well established, but religious explanations of life were rife. Darwin's theory certainly challenged this big-time!

Now, Darwin amassed countless facts--it was one of his incredible fortes. From these he inferred his theory, and on the face of it this would seem to be the scientific method if anything was. But the geologist and former friend and teacher of Darwin's, Adam Sedgwick, was rather incensed by the theory of evolution. Sedgwick was a seriously Christian believer, and could not abide this threat to all that he held dear. He lambasted Darwin, not explicitly because Darwin contradicted biblical explanations, but because Darwin's theory was (in our words) Aristotelian rather than Baconian: it was incorrect, old-fashioned and not real science at all!

Inverted pyramid, the Louvre

Sedgwick basically argued that Darwin inverted the proper pyramid of knowledge. He claimed to be using inductive reasoning by bringing to bear so many different facts to form a consistent theory. But in fact, argued Sedgwick, this was not induction at all! That's because Darwin used the outcome of life that he observed as if he could draw conclusions from it inductively, when in fact life had only progressed on the Earth once! Thus, Darwin was taking a single observation, partitioned into many minute facts to be sure, but was generalizing about life as if evolution were observed again and again. This, said Sedgwick, was old fashioned a priori theory driven reasoning that Aristotle would be proud of, but it did not have the empirical truth-value that the scientific method was developed to provide.

In various discussions of this topic then and since, it appears that Darwin largely conceded the formal point, but of course stuck to his guns. He could (and we can) predict new facts, but they are details that can immediately be fitted (or, Sedgwick would perhaps argue, be retro-fitted) into the theory. Yes, there was diversity in the world, but this could arise by other processes (such as special Creation) and the theory of evolution was not the only explanation as a result. It was not, argued Sedgwick, properly inductive.

One could argue that we have used this theory in so many ways, modeled mathematically and experimentally in artificial selection, to predict formerly unknown phenomena about life, that the theory has clearly stood the test of time. Many facts about the one process on earth, could be used to generalize about the process as if it could be repeated. We argue that different species in different places each do represent replicate observations from which the process of evolution can be induced. Or, one could argue, inductive reasoning is just one way of getting at convincing accounts of the nature of Nature.

One might even go all the way with Aristotle, and say that for the very reason that evolution did occur, our brains were adapted (by Darwinian processes!) so that we are built to understand Nature! The argument probably wouldn't hold much water, but it's a thought. In any case, the fact that evolution only occurred once does suggest that the idea was cooked up by Darwin in a non-inductive way--even if his theory was built upon countless observations, but of one single process.

The triumph of the Darwinian method, to use the title of a book by Michael Ghiselin that we posted on in October and November 2011, proliferates throughout the life sciences. There are things that this allows us to do that are not exactly inductive, but are close to inductive reasoning in many ways. This has to do with the nature of variation and how it's to be explained. In a next post we'll discuss this in light of DNA, totally unknown to Darwin. There are substantial problems, and many of the inferences we make about specifics of the past are speculative, but overall, Darwin was not a Madoff, and did not hustle us with a pyramid scheme!

We'll see how Darwinian concepts, more than any other, enable us to understand why DNA sequence can be 'random' on its own, in the sense that the A,C,G,T's along DNA are by various statistical tests random: the nucleotides in one place don't predict those nearby or elsewhere along the sequence. Yet the nucleotides are not just letters in a computer test, and are in fact anything but random. Indeed, the concept of randomness has to be revised because DNA sequences evolved.

It's, to me, rather elusive, and I need to read some more on this, which is on my urgent stack, if my university would ever leave me alonel ong enough to read it! But basically I think Sedgwick's idea is that Darwin seemed to agree that evolution only occurred once so that it is a kind of hypothesis that he developed, from observation, but not from induction. He didn't observe global evolution happening in many earths, for example, and indeed he never actually observed species evolving out of prior species.

Thus, he formed a theory and fit data to it, so to speak, but other kinds of theory could also fit the data. Darwin extrapolated from artificial selection as in agricultural (or pigeon) breeding, but that had never generated a new species. So this was an hypothesis without the proper foundation, the argument went.

See David Hull, "Darwin's svcience and Victorian philosophy of Science" in the Cambridge Companion to Darwin, if your university library has it (or I can send a reprint).

Evolution is deductive in that we predict many things about variation in life from the theory of evolution, and we attribute things to drift and selection and isolation and so on. But we didn't observe the same thing again and again. Selection and drift can produce similar results, and they are tested statistically, not like Newtonian forces that seem more clearly deterministic.

On the other hand, we observe the result of evolution all over the place (in snails, humans, frogs, trees) and in that sense, since the nature of the pattern is similar, I personally would say that was inductive reasoning to formulate an evolutionary theory.

So my point in this series is the immense power of the Darwinian approach, even if not everything is crystal clear, there are things we still strive to understand, and so on (as in any science). But without the Darwinian approach, our framework for understanding life is undermined--that is why so much of what we do goes back to evolution as the underlying explanation.

Later in the series we will talk about first the historical aspect of the method, and then the functional and adaptive application.

Holly, Sedgwick criticized Darwin for having devised his theory, and only then coming up with the facts to support it, rather than the other way around. That is, Sedgwick felt that Darwin didn't make all his observations, and then draw his conclusion -- induction -- but the other way around. As Sedgwick said, "I look on the theory as a vast pyramid resting on its apex, and that apex a mathematical point."

Of course Darwin did make and collect a lot of observations before he published his theory. But, Sedgwick's argument is that he didn't make his observations before he devised his theory. That is, his observations confirmed his theory, not lead to it.

From a letter from Sedgwick to Darwin, after reading Origin (the whole letter is here: http://www.darwinproject.ac.uk/entry-2548):

I have read your book with more pain than pleasure. Parts of it I admired greatly; parts I laughed at till my sides were almost sore; other parts I read with absolute sorrow; because I think them utterly false & grievously mischievous—f5 You have deserted—after a start in that tram-road of all solid physical truth—the the true method of induction—& started up a machinery as wild I think as Bishop Wilkin’s locomotive that was to sail with us to the Moon.f6 Many of your wide conclusions are based upon assumptions which can neither be proved nor disproved. Why then express them in the language & arrangements of philosophical induction?.— As to your grand principle—natural selection—what is it but a secondary consequence of supposed, or known, primary facts. Development is a better word because more close to the cause of the fact.

So, what did Darwin himself think about his methods? A quick search comes up with a 2009 paper by Francisco Ayala in PNAS -- "Darwin and the scientific method". Ayala says that Darwin claimed he used "true Baconian [inductive] principles and without any theory collected facts on a wholesale scale.” He also wrote, “How odd it is that anyone should not see that all observation must be for or against some view if it is to be of any service!”

But, Ayala says that what Darwin said he did and his actual practice were in contradiction. "Darwin claims to have followed the inductionist canon prevalent among British contemporary philosophers and economists, such as John Stuart Mill (1), and earlier authorities, notably the statesman and philosopher, Francis Bacon in his Novum Organum (2). The inductionist canon called for making observations without prejudice as to what they might mean and accumulating observations related to a particular subject so that a universal statement or conclusion could eventually emerge from them. Indeed, in one place in his Autobiography, Darwin affirms that he proceeded “on true Baconian principles and without any theory collected facts on a wholesale scale” (ref. 3, p. 119).

The facts are very different from these claims, however. Darwin's notebooks and private correspondence show that he entertained the hypothesis of the evolutionary transmutation of species shortly after returning from the voyage of the Beagle and, all important, that the hypothesis of natural selection occurred to him in 1838; several years before he claims to have allowed himself for the first time“to speculate on the subject.” Between the return of the Beagle on October 2, 1836, and publication of Origin of Species in 1859 (4) (and, indeed, until the end of his life), Darwin relentlessly pursued empirical evidence to corroborate the evolutionary origin of organisms and to test his theory of natural selection, which he saw as the explanatory process accounting for the adaptive organization of living beings and their diversification and change through time."

And indeed, he builds his argument in Origin so beautifully, his theory blossoming before our very eyes. But of course he knew where he was headed all along.

Does this perhaps fast and loose use of accepted methodology mean his conclusions are wrong? Of course not.

What this all shows is that science is a social endeavor without externally established rules of what counts towards an understanding of 'truth'. Induction, prediction, deduction, and so on are all part of it.

But, yes it sounds post-modern but it's true nonetheless, we operate largely on belief. We accept what we believe and try our damndest to prove it (not, contrary to widespread self-flattery, to falsify our ideas). We modify data or results, or stastically based decision-making to suit our predilections.

This what Thomas Kuhn and Ludwik Fleck argued essentially was how science worked. We never know when the next bend in the road will overturn some cherished idea. We never know if we're getting to 'the' truth (assuming there is such a thing), but we do get closer agreement between facts and ideas about them.

So was Sedgwick's argument that Darwin didn't collect ALL of his observations before forming the theory? It seems to me that collecting some of the facts and then developing a theory via inductive reasoning and then collecting more observations to test hypotheses derived from this theory wouldn't violate the scientific method. But from Ayala's article, it seems this is the crux of the argument.

I think Sedgwick's fundamental problem was that natural selection seems to take causation out of the hands of God. That is, his objections were primarily driven by his religious beliefs, even if he did in fact object to Darwin's methodology -- as Ken says, belief is behind much of the interpretation of science.

I have not yet read Ayala or Hull carefully enough, or looked at whatever Darwin correspondence and so on they cite. But on the face of it, it seems just as you say. Even if Darwin developed his hypotheses early after the Beagle, all that I know, from reading Voyage and his Geology books, and so on, is that he did as you say.

His 8 years on barnacles seem to have been a way for him to convince himself about his theory.

Anyway, from a philosophy and history of science point of view, as long as we accept that there are no rules for finding truth, and that there can be too-close adherence of a tribal kind, to theory as ideology, nonetheless it works (as I said in my previous comment)

I guess part of my confusion is my own limitation: I can't imagine a human being collecting observations while completely devoid of any theoretical bias/motivation. And if being a tabula rasa is the requirement for induction, then induction doesn't exist.

Well, at that time explorers were, for the first systematic time, collecting specimens and making observations of the world that hadn't been reported in European science. So, they had no preconception of what they'd find.

In fact, Darwin was a Christian when he started out, so the idea of explaining Nature as a 'process' would perhaps never have occurred to him (despite fragments of such speculation as in Lamarck or his uncle Erasmus, if he even knew of them at the time).

Even more than that, he only began to be influenced about uniformitarianism while reading Lyell, on the Beagle if I recall (and he may not have known about Hutton's work, or connected it to his trip's purpose). His main Beagle interests were in geology.

So he may simply not have been thinking as a 'scientist' (theory based) but really just as a collector of the unknown, until various aspects of pattern and so on occurred to him.

There had been other naturalists out collecting here and there, like von Humboldt and others who I wouldn't know of. But they were largely describing what they saw. The Beagle's mission was largely to survey the coast of South America for the Royal Navy,again a descriptive rather than 'scientific' endeavor.

I don't know what FitzRoy was thinking (he was a fundamentalist, that's well known), but he was a founder of modern meteorology, so he may or may not have been working on theories of atmosphere, humidity, and so on....and perhaps discussions over dinner in the officer's deck could have raised ideas about 'theory'.

We are so institutionalized in science these days, that we are taught theory in a sense even before facts, so that may mean we would have a hard time imagining a theory-free naturalist.

This is my endeavor to overhaul introductory bioanth! It's working wonderfully, imho. Observations first, then theory. All the textbooks frontload the theory which is a totally backwards way to teach people how to be learners. Again, imho.

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